The present invention relates to gasification methods and, more particularly, to fixed bed pressure gasification methods, oil gasification and flow gasification as well as disposal of waste materials.
The fixed bed pressure gasification operates with various carburizing materials including crude brown coal, brown coal briquettes, hard brown coal and mineral coal. The ash and water content of these materials fluctuates within broad limits. The preparation cost of these gasification materials is low.
The basic principle of fixed bed pressure gasification is described, for example, in W. Peters, "Kohlevergasung", Verlag Gluckauf GmbH, Essen. This principle is used as the basis for many fixed solid bed pressure gasification methods. Various modifications are disclosed, for example, in German Patent Documents DE-PS 2,640,180 and 2,732,544 in which a combination with a fluidized bed is proposed. In German Patent documents DD-PS 38791, 110297, 119814, 121796, 132980, 133818 and DE-PS 2,705,558 methods for efficiency increase, for liquid slag withdrawal, for lowering of the dust content of a crude gas formed in the method and for avoiding slag formation in the gasifier are described.
The main disadvantage of all practical methods is that the crude gas contains dust, high and low boiling hydrocarbons and water soluble organic compounds such as alcohol and aromatic compounds as well as their derivatives. Therefore expensive auxiliary devices are required for recovery and conversion of individual products as well as prevention of environmental damage.
German Patent document DD-PS 259,875 describes a proposed method for eliminating by-products. In this method the fuel height in the fixed bed pressure gasifier is lowered drastically. At temperatures of approximately 1000.degree. C. attained in the gas chamber, tar, oil and dust particles contained in the crude gas are converted in the gas chamber into crude gas. This method is not recommended because of safety considerations, since oxygen breakthrough can occur through the fixed bed in the gasifier which is at a very low height, which can cause a gas explosion in downstream units.
Also German Patent Document DD-PS 43253 describes a proposed method for converting liquid and solid components contained in the gas leaving the gasifier autooxidatively while gasification medium is fed into the gas. This process is not economically practical since a part of the product gas is burned. A reliable definite conversion of the liquid and solid components during this process is not guaranteed. Since this proposed method does not have any reliable post-operational teaching, the probability of gas explosions during processing must be considered.
German Patent Document DD-PS 150,475 describes a method in which higher hydrocarbons are converted by hydrocracking using a hydrogenation catalyst during post-gasification of the fixed bed pressure gasification crude gas. This method has the disadvantage that the entry temperature of the crude gas in the post-gasifier must be adjusted to the operational temperature of the catalyst. When brown coal is used in this gasification method, that can be accomplished only with complicated control and process techniques. An additional disadvantage of this method is the rapid poisoning of the catalyst with coal dust and ash particles entrained in the crude gas stream and therefore high operating costs. Furthermore German Published Patent Applications DE-OS 2,532,197 and 2,532,198 disclose proposed methods in which fixed bed pressure gasification crude gas is supplied with additional oxygen for post-gasification in a post-gasifier which contains a solid bed of inert or catalyst material so that gasification and cracking reactions occur in the post-gasification because of the temperature increase. This process is however disadvantageous because it is not possible to control crude gas composition and crude gas quantity in the post-gasifier. The solid bed height in the post-gasifier can result in efficiency decreases and stoppages of the gasification due to contamination with dust and ash.
Special waste materials are waste materials which originate from industrial and similar enterprises and public installations which are especially hazardous to health or especially damaging to air or water because of their type, properties or amounts. The primary industries producing special wastes are the chemical industry, the metalworking industry, the energy industry and waste industry. Sulfur-containing, hydrocarbon-containing and halogenated wastes are produced in the chemical industry. Oil emulsions, varnish slurries and galvanic wastes are produced by the metalworking industry. In thermal waste processing installations, e.g. for combustion and pyrolysis, partially loaded residues and flue and filter dusts in the areas of heat consumption and gas cleaning cause particular problems during their disposal. Particularly the contamination of these dusts with organic pollutants, such as dioxin and furan, as well as with heavy metals can cause severe environmental damage when these dusts are stored. For these and similar special wastes some proposed methods to process these wastes by bonding with clay-containing materials were disclosed in German Patent Documents 3,918,259, 3,713,482 and 3,919,011; or to process heavy metal containing residues to form solid storable products, such as described in German Patent Document DE-PS 3,502,215. In the case of the latter method, these products can be stored partially underground, but at very high cost.
Alternative methods include methods involving fusion or melting. Such methods are disclosed for example in the German Patent Documents DE-PS 3,939,344 and 3,206,984. The units or plants described in these Patent Documents require however a large amount of energy. They are still in the stage of laboratory and pilot plants and to reduce them to practice requires significant development efforts and time expenditures.
A proposed method known from gasification engineering and described in German Patent Document DD-PS 267,880 includes supplying an ash-containing liquid fuel separately and independently from a burner which is acted on with a dust-like fuel and the required oxygen for autothermal partial oxidation of the ash-containing liquid fuel by a coal dust burner of a gasification reactor, which is also fed steam via an inlet connector pipe. The gasification of the liquid waste occurs according to this method with a high consumption of coal dust which leads to high gas production costs. The amount of input liquid residues is very limited in this process.